Epitaxial and polycrystalline anatase films were grown by pulse-powered magnetron sputtering. The photoreduction of Ag ions showed the difference in the distribution of the photocatalytic active sites in these films. The polycrystalline anatase film was covered with an Ag layer. In contrast, discrete Ag particles were interspatially deposited on the epitaxial anatase film. Evaluation of the epitaxial film by micro-Raman spectrometry revealed that the rutile coexisted at only the site where the Ag particle was precipitated. These results suggest that the rutile/anatase interface is the active site for photocatalysis and is one of the dominant factors of the photocatalytic activity. (C) 2004 Elsevier B.V. All rights reserved.